In contemporary communication systems, connections, e.g. for voice, video or multimedia communication, are increasingly also being routed via packet-oriented communication networks, such as local area networks (LAN) or wide area networks (WAN). This technology forms the basis, for example, for “Internet telephony”, which is frequently also referred to as “Voice over Internet Protocol” (VoIP). In such packet-oriented communication networks, data to be transmitted are split into individual data packets provided with a transport address identifying the respective connection destination. This transport address is used to convey the data packets in the communication networks to the respective connection destination largely independently of one another.
At the present time, setup of voice, video or multimedia connections via a packet-oriented communication network is very often based on ITU-T recommendation H.323. The H.323 recommendation describes multimedia connections within a packet-oriented communication network and multimedia connections which are conveyed from a packet-oriented communication network via a gateway device to a circuit-switched communication network, e.g. an ISDN network, and from the latter on to a connection destination. However, such forwarding via a circuit-switched communication network does not use the advantageous infrastructure of existing packet-oriented communication networks, such as the Internet. Although the H.323 recommendation also discloses the practice of setting up H.323 connections from a source network to a destination network via a packet-oriented communication network, such connection setup on the basis of the prior art to date requires signaling between a “gatekeeper” in the source network and a “gatekeeper” in the destination network. Such signaling between various gatekeepers requires a high level of complexity for implementation, however, particularly when there are a plurality of packet-oriented communication networks between the source network and the destination network. In addition, it is necessary for the gatekeeper or the gateway device in the source network to manage and administer the addresses of all potential destination networks. In many cases, this requires an unusually high level of complexity, particularly for H.323 connections routed via the Internet, which can lead to connection destinations distributed all over the world.
Setup of voice, video or multimedia connections is frequently also based on the “SIP protocol” (SIP: Session Initiation Protocol) of the IETF forum (IETF: Internet Engineering Task Force). The SIP protocol also has the imperfections described above, however. The SIP protocol is disclosed, by way of example, in the document RFC 2543: “SIP: Session Initiation Protocol” by M. Handley, H. Schulzrinne, E. Schooler and J. Rosenberg, March 1999.